output more feature information in model file, #192

include/LightGBM/bin.h

 #ifndef LIGHTGBM_BIN_H_
 #define LIGHTGBM_BIN_H_
 
+#include <LightGBM/utils/common.h>
+
 #include <LightGBM/meta.h>
 
 #include <vector>
 #include <functional>
 #include <unordered_map>
+#include <sstream>
 
 namespace LightGBM {
 
@@ -150,8 +153,22 @@ public:
   * \param buffer The source
   */
   void CopyFrom(const char* buffer);
-
+  /*!
+  * \brief Get bin types
+  */
   inline BinType bin_type() const { return bin_type_; }
+  /*!
+  * \brief Get bin info
+  */
+  inline std::string bin_info() const {
+    if (bin_type_ == BinType::CategoricalBin) {
+      return Common::Join(bin_2_categorical_, ",");
+    } else {
+      std::stringstream str_buf;
+      str_buf << '[' << min_val_ << ',' << max_val_ << ']';
+      return str_buf.str();
+    }
+  }
 private:
   /*! \brief Number of bins */
   int num_bin_;
@@ -167,6 +184,10 @@ private:
   std::unordered_map<int, unsigned int> categorical_2_bin_;
   /*! \brief Mapper from bin to categorical */
   std::vector<int> bin_2_categorical_;
+  /*! \brief minimal feature vaule */
+  double min_val_;
+  /*! \brief maximum feature value */
+  double max_val_;
 };
 
 /*!

src/boosting/gbdt.cpp

@@ -109,6 +109,16 @@ void GBDT::ResetTrainingData(const BoostingConfig* config, const Dataset* train_
     label_idx_ = train_data->label_idx();
     // get feature names
     feature_names_ = train_data->feature_names();
+    // get feature infos
+    feature_infos_.clear();
+    for (int i = 0; i < max_feature_idx_ + 1; ++i) {
+      int feature_idx = train_data->GetInnerFeatureIndex(i);
+      if (feature_idx < 0) { 
+        feature_infos_.push_back("trival feature"); 
+      } else {
+        feature_infos_.push_back(train_data->FeatureAt(feature_idx)->bin_mapper()->bin_info());
+      }
+    }
   }
 
   if ((train_data_ != train_data && train_data != nullptr)
@@ -536,6 +546,12 @@ void GBDT::SaveModelToFile(int num_iteration, const char* filename) const {
   for (size_t i = 0; i < pairs.size(); ++i) {
     output_file << pairs[i].second << "=" << std::to_string(pairs[i].first) << std::endl;
   }
+
+  output_file << std::endl << "feature information:" << std::endl;
+  for (size_t i = 0; i < max_feature_idx_ + 1; ++i) {
+    output_file << feature_names_[i] << "=" << feature_infos_[i] << std::endl;
+  }
+
   output_file.close();
 }
 

src/boosting/gbdt.h

@@ -318,6 +318,8 @@ protected:
   int num_init_iteration_;
   /*! \brief Feature names */
   std::vector<std::string> feature_names_;
+  /*! \brief Feature informations */
+  std::vector<std::string> feature_infos_;
   /*! \brief number of threads */
   int num_threads_;
   /*! \brief Buffer for multi-threading bagging */

src/io/bin.cpp

@@ -83,7 +83,8 @@ void BinMapper::FindBin(std::vector<double>* values, size_t total_sample_cnt, in
     distinct_values.push_back(0);
     counts.push_back(zero_cnt);
   }
-
+  min_val_ = distinct_values.front();
+  max_val_ = distinct_values.back();
   int num_values = static_cast<int>(distinct_values.size());
   int cnt_in_bin0 = 0;
   if (bin_type_ == BinType::NumericalBin) {